WEDNESDAY, July 11 (HealthDay News) -- A new version of the prescription painkiller Oxycontin that makes the medication harder to abuse does not appear to reduce drug abuse. Instead, the drug seems to drive people toward more dangerous opioids, including heroin, a new study suggests.

Oxycontin has been popular among drug abusers since the mid-1990s, when a slow-release version entered the market. Although this version was supposed to discourage abuse because swallowing it did not give people a "high," it had the opposite outcome. The pills contained a larger dose of medicine, and people quickly figured out how to crush or dissolve them in water to snort or inject for an even bigger payoff, the study authors said.

"This had the effect of kicking off the epidemic of prescription-drug abuse that we have in this country right now," said Theodore Cicero, a psychiatry professor at Washington University in St. Louis and co-author of the new study.

The answer was an abuse-resistant Oxycontin, released in August 2010, which is formulated to make crushing or dissolving the pills in water all but impossible.

"There has been a reduction in the abuse of Oxycontin, which was, of course, the predicted ... effect," Cicero said. "We had some hypotheses that drug abusers would shift to [another opioid], but we didn't anticipate what would occur with heroin."

To explore how the new form of Oxycontin affects drug use, Cicero and his colleagues conducted surveys on patients who were at treatment centers for the abuse of prescription opioids for about a year and a half before and after the release of abuse-resistant Oxycontin. The researchers collected surveys from more than 2,500 patients at 150 drug treatment centers in 39 states.

The initial results of their study were published July 12 in the New England Journal of Medicine.

Whereas Oxycontin was the major opioid of abuse for almost 36 percent of the patients at the end of 2009 (the year before the newer form of Oxycontin was released), only 13 percent of patients reported that Oxycontin was the primary drug they abused in the beginning of 2012.

In contrast, the percentage of patients who said their drug of choice was another opioid, including the more potent fentanyl or hydromorphone, increased from 20 percent to 32 percent during this time.

Even more troubling, Cicero said, was the finding that the percentage of patients who reported using heroin in the past 30 days increased from 10 percent to 20 percent as the percentage using Oxycontin in the past month dropped from almost 50 percent to 30 percent.

The decline in Oxycontin use seems to be a reason for the uptick in heroin users, the authors said. Of the more than 2,500 patients, they followed 103 over the course of the study and asked them questions about their habits over the phone or online. One person responded that heroin is "easier to use, much cheaper and easily available."

"We are seeing a big upsurge in the use of heroin right now ... which is the last thing we need," Cicero said. It is harder for addicts to know the dose of heroin they are getting, they have to take it more frequently, they often start doing illicit activities to get money for heroin and they get into needle sharing, Cicero said.

Dr. Adam Bisaga, associate professor of psychiatry at Columbia University in New York City, said he doubts a lot of people would have switched to heroin because it became more difficult to abuse Oxycontin.

"People would probably not think twice about swallowing medication, but the thought of going to some shady neighborhood and getting heroin is not something that comes to mind," he said. "It's not the same market."

It might be more likely that people would take six Vicodin tablets to get the euphoric feeling that they would have got from one Oxycontin pill, Bisaga said, adding that doctors need to continue to be more vigilant about prescribing opioids only to patients who need them.

The switch to other opioids has its own risks, Cicero said. Addicts may have to try different doses to get the same high that Oxycontin gave them, and could end up overdosing.

One way to discourage the switch to other opioids would be to develop more slow-release versions that cannot be swallowed for a high, Cicero said. Unlike Oxycontin, prescription opioids like Vicodin contain acetaminophen (Tylenol), which makes them less desirable to snort because they can be irritating. There is, however, a "very grave concern" that this would push more people to heroin use, Cicero said.

"If you deter the use of one particular compound, they are not going to stop taking drugs," Cicero said. Every one of the 103 patients who filled out longer surveys said they would replace Oxycontin with something else.

Instead of focusing our attention on stemming opioid supply, the government, scientists and drug makers need to work on ending demand, Cicero said. Many of the people who end up in treatment centers for opioid abuse started abusing when they were 14 or 15 years old, he added.

Steps could be taken to reduce demand through school programs that teach about opioids, advertisements that put opioid addiction in the same light as crack and cocaine, and better diagnosis of children who are depressed or anxious who may be more likely to start taking opioids, Cicero said.